Mullerian inhibiting substance promotes interferon gamma-induced gene expression and apoptosis in breast cancer cells

This report demonstrates that in addition to interferons and cytokines, members of the TGF beta superfamily such as Mullerian inhibiting substance (MIS) and activin A also regulate IRF-1 expression. MIS induced IRF-1 expression in the mammary glands of mice in vivo and in breast cancer cells in vitro and stimulation of IRF-1 by MIS was dependent on activation of the NF kappa B pathway. In the rat mammary gland, IRF-1 expression gradually decreased during pregnancy and lactation but increased at involution. In breast cancer, the IRF-1 protein was absent in 13% of tumors tested compared with matched normal glands. Consistent with its growth suppressive activity, expression of IRF-1 in breast cancer cells induced apoptosis. Treatment of breast cancer cells with MIS and interferon gamma (IFN-gamma) co-stimulated IRF-1 and CEACAM1 expression and synergistic induction of CEACAM1 by a combination of MIS and IFN-gamma was impaired by antisense IRF-1 expression. Furthermore, a combination of IFN-gamma and MIS inhibited the growth of breast cancer cells to a greater extent than either one alone. Both reagents alone significantly decreased the fraction of cells in the S-phase of the cell cycle, an effect not enhanced when they were used in combination. However, MIS promoted IFN-gamma-induced apoptosis demonstrating a functional interaction between these two classes of signaling molecules in regulation of breast cancer cell growth.     

Mullerian inhibiting substance regulates NFkappaB signaling and growth of mammary epithelial cells in vivo

Müllerian inhibiting substance (MIS) inhibits breast cancer cell growth in vitro through interference with cell cycle progression and induction of apoptosis, a process associated with NFkappaB activation and up-regulation of one of its important target genes, IEX-1S (Segev, D. L., Ha, T., Tran, T. T., Kenneally, M., Harkin, P., Jung, M., MacLaughlin, D. T., Donahoe, P. K., and Maheswaran, S. (2000) J. Biol. Chem. 275, 28371-28379). Here we demonstrate that MIS activates the NFkappaB signaling cascade, induces IEX-1S mRNA, and inhibits the growth of MCF10A, an immortalized human breast epithelial cell line with characteristics of normal cells. In vivo, an inverse correlation was found to exist between various stages of mammary growth and MIS type II receptor expression. Receptor mRNA significantly diminished during puberty, when the ductal system branches and invades the adipose stroma and during the expansive growth at lactation, but it was up-regulated during involution, a time of regression and apoptosis. Peripartum variations in MIS type II receptor expression correlated with NFkappaB activation and IEX-1S mRNA expression. Administration of MIS to female mice induced NFkappaB DNA binding and IEX-1S mRNA expression in the breast. Furthermore, exposure to MIS in vivo increased apoptosis in the mouse mammary ductal epithelium. Thus, MIS may function as an endogenous hormonal regulator of NFkappaB signaling and growth in the breast.     

Mullerian inhibiting substance inhibits breast cancer cell growth through an NFkappa B-mediated pathway

Müllerian inhibiting substance (MIS), a member of the transforming growth factor-beta superfamily, induces regression of the Müllerian duct in male embryos. In this report, we demonstrate MIS type II receptor expression in normal breast tissue and in human breast cancer cell lines, breast fibroadenoma, and ductal adenocarcinomas. MIS inhibited the growth of both estrogen receptor (ER)-positive T47D and ER-negative MDA-MB-231 breast cancer cell lines, suggesting a broader range of target tissues for MIS action. Inhibition of growth was manifested by an increase in the fraction of cells in the G(1) phase of the cell cycle and induction of apoptosis. Treatment of breast cancer cells with MIS activated the NFkappaB pathway and selectively up-regulated the immediate early gene IEX-1S, which, when overexpressed, inhibited breast cancer cell growth. Dominant negative IkappaBalpha expression ablated both MIS-mediated induction of IEX-1S and inhibition of growth, indicating that activation of the NFkappaB signaling pathway was required for these processes. These results identify the NFkappaB-mediated signaling pathway and a target gene for MIS action and suggest a putative role for the MIS ligand and its downstream interactors in the treatment of ER-positive as well as negative breast cancers.     

Circadian clock gene expression regulates cancer cell growth through glutaminase

Glutamine is an essential amino acid for malignant tumor cells. Glutaminase that metabolizes glutamine reaches a maximum expression in tumors immediately before the maximum proliferation rate. Tumor cells grow at different rates during the day. We postulated that the activity of glutaminase in tumor cells is subject to the regulation of circadian clock gene. We measured glutaminase by western blot analysis and circadian clock gene expression by real-time polymerase chain reaction in the liver and tumor cells at six equispaced time points of the day in individual mice of a 12/12 h light/dark schedule. The results showed that the tumor-bearing mice, under normal diurnal conditions, are circadianly entrained, as reflected by the normal host locomotor activity rhythms and rhythmic liver clock gene expression. The tumors within these mice are also circadianly organized, as reflected by circadian clock gene （Bmall） expression. What is most remarkable is that kidney-type glutaminase also showed circadian rhythms in the same pattern with tumor circadian clock gene expression in liver cancer xenograft model, indicating that conditionally inhibiting glutaminase activity may provide a new target for cancer therapy.     

Amyloid precursor protein regulates migration and metalloproteinase gene expression in prostate cancer cells

Amyloid precursor protein (APP) is a type I transmembrane protein, and one of its processed forms, β-amyloid, is considered to play a central role in the development of Alzheimer’s disease. We previously showed that APP is a primary androgen-responsive gene in prostate cancer and that its increased expression is correlated with poor prognosis for patients with prostate cancer. APP has also been implicated in several human malignancies. Nevertheless, the mechanism underlying the pro-proliferative effects of APP on cancers is still not well-understood. In the present study, we explored a pathophysiological role for APP in prostate cancer cells using siRNA targeting APP (siAPP). The proliferation and migration of LNCaP and DU145 prostate cancer cells were significantly suppressed by siAPP. Differentially expressed genes in siAPP-treated cells compared to control siRNA-treated cells were identified by microarray analysis. Notably, several metalloproteinase genes, such as ADAM10 and ADAM17, and epithelial–mesenchymal transition (EMT)-related genes, such as VIM, and SNAI2, were downregulated in siAPP-treated cells as compared to control cells. The expression of these genes was upregulated in LNCaP cells stably expressing APP when compared with control cells. APP-overexpressing LNCaP cells exhibited enhanced migration in comparison to control cells. These results suggest that APP may contribute to the proliferation and migration of prostate cancer cells by modulating the expression of metalloproteinase and EMT-related genes.     

Localization of Mullerian inhibiting substance receptors in various human cancer cell lines

Recombinant human MIS (rhMIS) produced in transfected Chinese hamster ovary cells has been purified by immunoaffinity chromatography. In the absence of reducing agents, 140 kD homodimer and several oligomers with molecular masses from 280 to 1000 kD are present. Homodimer, tetramer, and higher-molecular-weight rhMIS fractions reduced survival of tumor cells. For these experiments, FITC-labeled rhMIS was used for binding and endocytosis studies by flow cytometry. Flow cytometry performed on MIS-sensitive cancer cell lines demonstrated specific binding of rhMIS. The majority of rhMIS receptors have cytosolic localization. Thus, the level of MIS receptors on the cell membrane was proportional to the content of MIS-binding proteins in the whole cell and defines a level of receptor-mediated endocytosis. The immunopurified rhMIS caused significant growth inhibition of ovarian and prostate adenocarcinoma and melanoma human cell lines in inhibition assays.     

Activation of NADPH oxidase by transforming growth factor-beta in hepatocytes mediates up-regulation of epidermal growth factor receptor ligands through a nuclear factor-kappaB-dependent mechanism

The TGF-beta (transforming growth factor-beta) induces survival signals in foetal rat hepatocytes through transactivation of EGFR (epidermal growth factor receptor). The molecular mechanism is not completely understood, but both activation of the TACE (tumour necrosis factor alpha-converting enzyme)/ADAM17 (a disintegrin and metalloproteinase 17; one of the metalloproteases involved in shedding of the EGFR ligands) and up-regulation of TGF-alpha and HB-EGF (heparin-binding epidermal growth factor-like growth factor) appear to be involved. In the present study, we have analysed the molecular mechanisms that mediate up-regulation of the EGFR ligands by TGF-beta in foetal rat hepatocytes. The potential involvement of ROS (reactive oxygen species), an early signal induced by TGF-beta, and the existence of an amplification loop triggered by initial activation of the EGFR, have been studied. Results indicate that DPI (diphenyleneiodonium) and apocynin, two NOX (NADPH oxidase) inhibitors, and SB431542, an inhibitor of the TbetaR-I (TGF-beta receptor I), block up-regulation of EGFR ligands and Akt activation. Different members of the NOX family of genes are expressed in hepatocytes, included nox1, nox2 and nox4. TGF-beta up-regulates nox4 and increases the levels of Rac1 protein, a known regulator of both Nox1 and Nox2, in a TbetaR-I-dependent manner. TGF-beta mediates activation of the nuclear factor-kappaB pathway, which is inhibited by DPI and is required for up-regulation of TGF-alpha and HB-EGF. In contrast, EGFR activation is not required for TGF-beta-induced up-regulation of those ligands. Considering previous work that has established the role of ROS in apoptosis induced by TGF-beta in hepatocytes, the results of the present study indicate that ROS might mediate both pro- and anti-apoptotic signals in TGF-beta-treated cells.     

Autocrine transforming growth factor-beta signaling mediates Smad-independent motility in human cancer cells

Transforming growth factor-beta (TGF-beta) is a pleiotropic growth factor that plays a critical role in modulating cell growth, differentiation, and plasticity. There is increasing evidence that after cells lose their sensitivity to TGF-beta-mediated growth inhibition, autocrine TGF-beta signaling may potentially promote tumor cell motility and invasiveness. To understand the molecular mechanisms by which autocrine TGF-beta may selectively contribute to tumor cell motility, we have generated MDA-MB-231 breast cancer cells stably expressing a kinase-inactive type II TGF-beta receptor (T beta RII-K277R). Our data indicate that T beta RII-K277R is expressed, can associate with the type I TGF-beta receptor, and block both Smad-dependent and -independent signaling pathways activated by TGF-beta. In addition, wound closure and transwell migration assays indicated that the basal migratory potential of T beta RII-K277R expressing cells was impaired. The impaired motility of T beta RII-K277R cells could be restored by reconstituting TGF-beta signaling with a constitutively active TGF-beta type I receptor (ALK5(TD)) but not by reconstituting Smad signaling with Smad2/4 or Smad3/4 expression. In addition, the levels of ALK5(TD) expression sufficient to restore motility in the cells expressing T beta RII-K277R were associated with an increase in phosphorylation of Akt and extracellular signal-regulated kinase 1/2 but not Smad2. These data indicate that different signaling pathways require different thresholds of TGF-beta activation and suggest that TGF-beta promotes motility through mechanisms independent of Smad signaling, possibly involving activation of the phosphatidylinositol 3-kinase/Akt and/or mitogen-activated protein kinase pathways.     

灵芝酸A对前列腺癌LNCaP细胞的生长抑制作用及机制

本研究利用alamarBlue~?测定细胞活力法、流式细胞术(annxin V-FITC)/PI双染色测定细胞凋亡法和高效液相色谱(high performance liquid chromatography,HPLC)测定5α-还原酶活性法评价灵芝酸A对前列腺癌的体外抗肿瘤活性,并进一步利用流式细胞术2’,7’-二氯荧光素二乙酸酯(2’,7’-dichlorofluorescindiacetate,H2DCFDA)染色测定ROS释放量法、实时荧光定量PCR(quantitative real-time PCR,qPCR)和蛋白质免疫印迹(western blot,WB)检测雄激素受体(androgen receptor,AR)基因和凋亡相关基因表达的方法,探讨其作用机理。研究结果表明灵芝酸A可通过抑制5α-还原酶活性,抑制睾酮诱导的前列腺癌LNCaP细胞增殖,诱发细胞早期凋亡来发挥抗肿瘤活性;进一步研究表明,灵芝酸A降低前列腺癌细胞中AR的表达,并通过引发细胞线粒体功能障碍释放过量活性氧(reactive oxygen species,ROS)诱发细胞凋亡,而qPCR和WB的数据进一步表明细胞线粒体功能障碍与抑癌基因caspase-3、bad和aifm1的高表达密切相关。     

Angiotensin II induces matrix metalloproteinase-9 expression via a nuclear factor-kappaB-dependent pathway in vascular smooth muscle cells

Angiotensin II (AngII) is widely recognized as a critical regulator of the development of atherosclerosis. Matrix metalloproteinases (MMPs) are thought to participate in plaque destabilization through degradation of the extracellular matrix. In the present study, we investigated the potential mechanism of AngII-induced MMP-9 expression in vascular smooth muscle cells (VSMC). AngII upregulated the expression of MMP-9 significantly in VSMC obtained from rat aorta. RNAi-mediated knockdown of p65 and losartan, an inhibitor of AngII receptors subtype-1 (AT₁), could abolish AngII-induced MMP-9 expression. In addition, AngII induced the NF-κB binding activity via AT₁ and AT₂ receptors in VSMC, and AngII-induced activation of NF-κB is not associated with significant downregulation of IκB. In summary, this study demonstrates that AngII stimulates NF-κB nuclear translocation in VSMC via AT₁ and AT₂. AngII increases the expression of MMP-9 in VSMC, and AT₁ and NF-κB pathways have an important role in this response.     

Sig1R protein regulates hERG channel expression through a post-translational mechanism in leukemic cells

Sig1R (Sigma-1receptor) is a 25-kDa protein structurally unrelated to other mammalian proteins. Sig1R is present in brain, liver, and heart and is overexpressed in cancer cells. Studies using exogenous sigma ligands have shown that Sig1R interacts with a variety of ion channels, but its intrinsic function and mechanism of action remain unclear. The human ether-à-gogo related gene (hERG) encodes a cardiac channel that is also abnormally expressed in many primary human cancers, potentiating tumor progression through the modulation of extracellular matrix adhesive interactions. We show herein that sigma ligands inhibit hERG current density and cell adhesion to fibronectin in K562 myeloid leukemia cells. Heterologous expression in Xenopus oocytes demonstrates that Sig1R potentiates hERG current by stimulating channel subunit biosynthesis. Silencing Sig1R in leukemic K562 cells depresses hERG current density and cell adhesion to fibronectin by reducing hERG membrane expression. In K562 cells, Sig1R silencing does not modify hERG mRNA contents but reduces hERG mature form densities. In HEK cells expressing hERG and Sig1R, both proteins co-immunoprecipitate, demonstrating a physical association. Finally, Sig1R expression enhances both channel protein maturation and stability. Altogether, these results demonstrate for the first time that Sig1R controls ion channel expression through the regulation of subunit trafficking activity.